This invention relates to stabilization of oxidizable organic materials with polymeric benzenoid hydroquinoids. This invention also relates to polymeric benzenoid hydroquinoids as new chemicals as well as to the oxidative stabilization of foodstuffs and organic materials subject to the deleterious effects of oxidative deterioration. These benzenoid hydroquinoid compounds are generally useful as antioxidants and age resistors for the preservation of materials which deteriorate in the presence of oxygen and on aging, and are particularly valuable as antioxidants for vegetable oils and fats for edible use.
Oxidation of fats and oils in consumable (edible) materials is an especial problem as such oxidation can render foodstuffs unpalatable and unfit for consumption. Of the three major components of edible materials which are protein, carbohydrates and lipids (which include fats and oils), lipids, i.e., the fats and oils, are most subject to oxidative degradation.
A variety of materials have been proposed as additives to inhibit undesired oxidation. Typically, these materials have a hydroquinone or phenolic structure. Among those commonly used are butylated hydroxy anisole (BHA) and butylated hydroxy toluene (BHT). BHA and BHT are readily soluble in fats and oils, are considered to be non-toxic and can be used in small quantities to inhibit or retard rancidity. However, the use of BHA and BHT is under attack since upon ingestion with foods these materials pass through the gastrointestinal tract walls into the blood stream and vital organs where their presence and safety to the host body is alleged to be of doubtful consequence. Observed pathological effects, carcinogenic potential, interactions with enzymes and lipids, effects on reproduction (Branen, A. L., J.O.A.C.S. 52:59 (1975)) have indicated the long-term safety of BHA and BHT is at least subject to controversy.
Other important considerations besides toxicity in applying antioxidants to vegetable oils to achieve optimum results are that the antioxidant not contribute an objectionable odor, color or flavor, and have complete solubility in the fats and oils at treatment levels sufficient to obtain good stability results. An increased antioxidant activity with complete solubility permits lower treatment levels. Accordingly, it is becoming recognized that any new approach to the problem of incorporating antioxidant materials in edibles requires a neat balancing of desirable characteristics which cannot be predicted on the basis of chemical structure.
In the prior art, Sommabend, U.S. Pat. No. 3,128,259 teaches the concept of preparing synthetic polymeric resins containing phenolic hydroxyl groups which are further reacted to prepare polyhydric alcohols adapted to prepare drying-oil esters and alkyl resins. Hunter, U.S. Pat. No. 3,424,821 teaches a composition wherein di(secondary alkyl) hydroquinones are reacted with a polymer such as styrene to obtain antioxidants suitable for polymers or vegetable oils. Zaffaroni, U.S. Pat. No. 3,994,828 teaches that fixing an antioxidant phenolic moiety to a polymer molecule of sufficient size to prevent passage through the walls of the gastrointestinal tract provides an antioxidant suitable for substantial nonabsorbtion from the gastrointestinal tract. Dale et al., U.S. Pat. No. 3,930,047, teaches monohydroxy polystyrene polymeric phenolic antioxidants which could easily be varied in molecular size to achieve desired nonabsorption through the walls of the intestinal tract. The materials of '047 are homopolymers of alpha-(2-hydroxy-3,5-di-lower alkylphenyl) ethylvinyl benzene or alpha-(2-hydroxy-3-lower alkylphenyl)ethylvinyl benzene which exhibit antioxidant activity in fats, oils and other foodstuffs. The antioxidants of '047 are monohydroxy compounds. Dale et al., U.S. Pat. No. 3,996,160, teaches ring polymerized hydroquinoid polymers having antioxidant activity for foods wherein the polymers are prepared from the copolymerization of a diolefinic hydrocarbon, a hydroquinoid and optionally a phenolic. The olefinic hydrocarbon preferably is a divinylbenzene, the hydroquinoid is preferably hydroquinone and other 1,4-dihydroxybenzenes. Suitable phenolic compounds are phenol, cresols, dimethyl, ethyl and butylphenols as well as bisphenol-A. Use of a solvent is indicated in Example IX of '160 in a blend of cottonseed and soybean oil, the sample containing 0.5 ml benzene to 50 ml vegetable oil. Th phenolic moieties are not of the polymeric chain but attach as separate moieties to the hydroquinone moiety. Wang et al., U.S. Pat. No. 3,996,198 teaches what is essentially a linear polymer prepared from preferably divinylbenzenes, phenolic reactants preferably such as phenol, the cresols, dimethyl ethyl and butyl phenols. The polymer of '198, according to the depicted structure, contains one equivalent of aromatic moiety which does not contribute antioxidant activity to the polymer since it is void of functional groups. Use of a solvent is indicated in Example VIII of '198 in a blend of cottonseed oil and soybean oil, the sample containing 0.5 ml benzene to 50 ml vegetable oil. Similar compounds for antioxidant use are taught in U.S. Pat. Nos. 3,996,199 and 4,054,676 wherein polymeric antioxidants are prepared from vinylbenzenes, a hydroquinone and certain phenolic compounds.
Accordingly a number of polymeric antioxidants have been prepared which are distinguished by the moieties contained in the polymer molecules, methods of preparation and consequent properties. However, as a rule, many of the antioxidants are not markedly superior in their antioxidant and other properties to BHT and BHA.
Since it is known from the prior art that hydroquinones such as tert-butylhydroquinone have been used as antioxidants in edibles, it is a primary object of this invention to provide a compound wherein the hydroquinone moiety with its antioxidant properties is contained in repeating units of the polymer chain. Another object is to provide a compound with antioxidant properties superior to BHT and BHA wherein the molecule is soluble in fats and vegetable oils and is of sufficient molecular size as to achieve nonabsorption through the walls of the gastrointestinal tract. Other objects appear hereinafter.